Re: Chevy OE cranks, cyl. heads.
 

Billy, My buddies at Brodix tell me that as their Core boxes wear the port is cast smaller.
I was questioning them one day about their advertisement for port size and flow. I told them that what I buy never matches the advertised size and flow.
Dave Roder told me it was because all the ads are done off the first production run and as they pour/cast more heads the ports get smaller.
I'm no foundry expert so I just shut up and accepted the explanation.
Probably what they wanted me to do, LoL.
I would bet that the GM X means the mold/core box was modified. If the X was for worn out why would they be using them? No doubt the X castings I've seen always seem to have more intake volume.

Re: Chevy OE cranks, cyl. heads.
 

Has anyone ever seen a '61 or '62 date code 461 casting that was NOT a 461X? I haven't and I have seen 20 or 30 of them in junk yards.

Re: Chevy OE cranks, cyl. heads.
 

Dwight, according to the source below and other sources the 461 and 461X casting numbers date back to 1961 (first 327 engines).

http://www.corvetteactioncenter.com/...gines-286.html

http://www.chevytech.com/3c3782461.html

Re: Chevy OE cranks, cyl. heads.
 

Interesting,
No 22542525 heads on the list.
Olds Nascar head/